Sunlight Simulator Apparatus

ABSTRACT

Sunlight simulators that have optical homogenizer units that provide adjustably positionable beams of radiation, each within a selected portion of the spectrum of wave lengths of radiation emitted from a light source, that have uniform output intensity profiles measured across the ends of the optical homogenizer units. These sunlight simulators include either liquid light guides or fiber optic light guides that conduct the beams of radiation, developed from the light source, to the optical homogenizer units. Dosage regulating means control the doses of radiation provided by the optical homogenizer units.

RELATED APPLICATIONS

This application is a divisional application of application Ser. No.11/366,272 filed Mar. 2, 2006.

FIELD OF THE INVENTION

The present invention relates, in general, to simulating light and, inparticular, to apparatus for simulating sunlight for sunburn studies,materials testing, component testing, and other purposes.

BACKGROUND OF THE INVENTION

The sunlight spectrum includes the ultraviolet, visible, and infraredlight wavelength ranges. Various types of equipment have been developedthat simulate one or more of these light frequency ranges and are usedin performing various tests, for example, on humans or materials orcomponents to determine the effect of these light wavelength ranges onhumans or materials or components.

It is well known that exposure to ultraviolet radiation can causeadverse skin conditions, including skin cancers. The predominant sourceof the ultraviolet radiation is sunlight radiation. Various sunscreenformulations that are applied to the skin are available to reduce oreliminate the adverse effect of sunlight on humans and variousequipments used in testing the effectiveness of such sunscreenformulations (i.e., the skin reactions to various ultraviolet doses) todetermine the Sunscreen Protection Factor (SPF) are available.

Test apparatus of this type that is available at the present timeincludes an artificial light source that provides (a) a single beam ofselected intensity focused upon a subject to test skin reaction to theintensity of the single beam of ultraviolet radiation, or (b) aplurality of beams of various selected intensities focusedsimultaneously upon a subject to test simultaneously skin reaction tothe various intensities of the plurality of beams of ultravioletradiation.

In general, the skin reaction test units that are currently availablefail to satisfy a number of the requirements of the users of such units.Some fail to provide beams of radiation having the desired uniformoutput intensity profiles, so that often it is difficult for the user toproperly quantify and qualify the test results. Some fail to provide theusers of the test units with sufficient flexibility to conduct the typesof tests the users would like to conduct in an easy and efficient mannerthat provide accurate and repeatable results.

Yet another problem with currently available skin reaction test units isthe thermal discomfort that can be experienced by certain subjectsduring exposure that is caused by the presence of certain wavelengths inthe radiation to which the subject is exposed. Despite efforts toeliminate, for example, infrared radiation from the lamp source by theinclusion, for example, of dichroic mirrors and blocking filters, thetest subjects still can be exposed, under certain conditions, to anundesirable level of infrared radiation that is not eliminated from thebeams of radiations to which the test subject is exposed and, thereby,be exposed to undesirable thermal discomfort.

As to test units that are available to determine the effect of sunlighton materials and components (e.g., photovoltaic cells), many are subjectto the same general criticism set out above with respect to the skinreaction test units. Some fail to provide the user with test resultsthat are properly quantified and qualified, while others lack theflexibility to conduct the types of tests the users would like toconduct in an easy and efficient manner that provide accurate results.

SUMMARY OF THE INVENTION

Accordingly, one sunlight simulator, constructed in accordance with thepresent invention, includes a housing, a light source positioned withinthe housing, and light collecting means for developing from radiationemitted from the light source a plurality of beams of radiation, eachwithin a selected portion of the spectrum of wave lengths of radiationemitted from the light source. This sunlight simulator also includes aplurality of light guides, each positioned to receive individually fromthe light collecting means one of the beams of radiation, for conductingthe beams of radiation away from the light collecting means. A pluralityof optical homogenizer units, each positioned to receive individuallyfrom one of the light guides one of the beams of radiation, provide aplurality of adjustably positionable beams of radiation having uniformoutput intensity profiles measured across the ends of the opticalhomogenizer units. Dosage regulating means control the doses ofradiation provided by the optical homogenizer units.

Another sunlight simulator, constructed in accordance with the presentinvention, includes a housing, a light source positioned within thehousing, and light collecting means for developing from radiationemitted from the light source a beam of radiation within a selectedportion of the spectrum of wave lengths of radiation emitted from thelight source. This sunlight simulator also includes a fiber optic lightguide positioned to receive from the light collecting means the beam ofradiation for conducting the beam of radiation away from the lightcollecting means. An optical homogenizer unit, positioned to receivefrom the fiber optic light guide the beam of radiation, provides anadjustably positionable beam of radiation having a uniform outputintensity profile measured across the end of the optical homogenizerunit. Dosage regulating means control the dose of radiation provided bythe optical homogenizer unit.

Another aspect of the present invention is an optical homogenizer unitthat includes an elongated tube of circular cross section, a multisidedelongated optical homogenizer having a length equal to the length of thetube and positioned within the tube, and filler material in the spacesbetween the longitudinal surfaces of the optical homogenizer and theinner surface of the tube.

Yet another aspect of the present invention is dosage regulatingapparatus for a sunlight simulator for controlling the doses ofradiation developed by the sunlight simulator. This apparatus includes asensor for monitoring the intensity of a beam of radiation developed bythe sunlight simulator and control means responsive to the sensor forblocking the passage of the beam of radiation when the dose of radiationdeveloped by the sunlight simulator reaches a preset level.

A further aspect of the present invention is attenuator apparatus for asunlight simulator for controlling the intensity of a beam of radiationdeveloped by the sunlight simulator. This apparatus includes anattenuator having through openings that vary in size to vary theintensity of a beam of radiation passing through the attenuator andmeans for moving the attenuator to selectively regulate the intensity ofthe beam of radiation passing therethrough.

A still further aspect of the present invention is a sunlight simulatorprobe that has a block adapted to contact the skin of a subject to whichradiation from the probe is to be provided. The block includes a heatsink for relieving heat generated by artifact infrared radiation andheat dispelled by the block, an electrically polar oriented coolingsource having a surface facing the subject and sensing means fordeveloping an indication of the skin temperature of the subject forcontrolling the temperature of the cooling source, and a high dielectricpolymer front cover having a high resistance to electrical transmission,high thermal conductivity, and a window through which the sensing meansin the cooling source are exposed to the skin of the subject. This probefurther includes means responsive to the sensing means for controllingthe temperature of the cooling source.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1, partially in cross-section and partially in explodedperspective, illustrates a first embodiment of a sunlight simulator,constructed in accordance with the present invention, in which the lightguides are liquid light guides.

FIG. 2 is a cross-sectional view that illustrates a portion of the FIG.1 sunlight simulator on an enlarged scale and in greater detail.

FIG. 3 is a cross-sectional view taken along lines 3-3 of FIGS. 1 and 2.

FIG. 4, partially in cross-section and partially in explodedperspective, illustrates a second embodiment of a sunlight simulator,constructed in accordance with the present invention, in which the lightguides are fiber optic light guides.

FIGS. 5A and 5B are exploded perspective views that illustrate portionsof the FIG. 1 sunlight simulator and the FIG. 4 sunlight simulator on anenlarged scale and in greater detail and at different stages ofoperation of the dosage regulating apparatus and attenuator apparatus ofthe present invention.

FIG. 6 is a cross-sectional view of an optical homogenizer unitconstructed in accordance with the present invention.

FIG. 7 is a perspective view of an optical quartz disc that serves as asensor in the dosage regulating apparatus of the present invention.

FIG. 8 is a perspective view of a second form of an attenuator for usein the attenuator apparatus illustrated in FIGS. 5A and 5B.

FIGS. 9A and 9B are perspective views of a third form of an attenuatorfor use in the attenuator apparatus illustrated in FIGS. 5A and 5B atdifferent stages of operation of the of the shutter.

FIG. 10 is a perspective view of the probe end of a sunlight simulatorconstructed in accordance with the present invention.

FIG. 10A is an exploded perspective view of a portion of the FIG. 10probe end of a sunlight simulator.

DETAILED DESCRIPTION OF THE INVENTION

In the drawings, like reference numerals represent like elements.

Referring to FIGS. 1, 2, 3, and 4, a sunlight simulator, constructed inaccordance with the present invention, includes a housing 12 and a lightsource 14 positioned within housing 12. For the embodiment of theinvention illustrated, housing 12 is cylindrical, having an upperportion 12 a and a lower portion 12 b, and is substantially light tightexcept as hereinafter described to allow the escape of light in acontrolled manner.

Light source 14 is disposed in the upper portion 12 a of housing 12along the central axis 12 c of the housing. Light source 14 is anartificial light source, preferably a xenon short arc lamp or such otherhigh intensity lamp, that emits a substantial amount of radiation,including radiation in the ultraviolet range.

Also included in a sunlight simulator, constructed in accordance withthe present invention, are light collecting means for developing fromradiation emitted from lamp 14 a plurality of beams of radiation, eachwithin a selected portion of the spectrum of wave lengths of radiationemitted from the lamp. As will be understood from further descriptionbelow of the present invention, the intensity of each beam of radiationdeveloped by the light collecting means is individually and selectivelyadjustable.

In the embodiment of the present invention illustrated in FIGS. 1, 2,and 3, the light collecting means surround lamp 14 and include aplurality of light collecting assemblies 16 that are positioned radiallyoutward from lamp 14. In particular, each light collecting assembly 16includes a collimating lens assembly, composed of a pair of opposedconvex lenses 18 and 20 for the embodiment of the present inventionillustrated, that is spaced radially outward from lamp 14. A single lensthat performs the collimating function may be substituted for the pairof opposed convex lenses 18 and 20. Each collimating lens assemblydirects a portion of the radiation emitted from lamp 14 radiallyoutward.

Each light collecting assembly 16 also includes a mirror 22 associatedwith the collimating lens assembly and in substantial radial alignmentwith the associated collimating lens assembly. Each mirror 22 issubstantially equidistantly spaced from the associated collimating lensassembly. Preferably, each mirror 22 is a dichroic mirror and, as bestillustrated in FIGS. 1 and 2, is disposed at an angle with respect tothe radius of lamp 14, which is 45° for the embodiment of the presentinvention being described. The collimating lens assemblies andassociated mirrors are equally spaced apart radially around lamp 14 andequally spaced outwardly from the lamp.

Each mirror 22 reflects vertically downward, in a path substantiallyparallel to central axis 12 c of housing 12, only a portion of thespectrum of optical energy directed to the mirror from the associatedcollimating lens assembly. For the embodiment of the present inventionbeing described, dichroic mirrors 22 predominantly reflect ultravioletradiation vertically downward, while other portions of the spectrum aretransmitted onto the inner surface of the housing that serves as a heatsink. As a result, for the embodiment of the present invention beingdescribed, six parallel and equidistantly spaced beams of ultravioletradiation are provided by the apparatus thus far described.

For the sunlight simulator being described, the light collecting means,preferably, further include a plurality of blocking filters 24, oneassociated with each dichroic mirror 22 and in the path of the radiationreflected by the associated dichroic mirror, for removing shortultraviolet radiation (below 290 nm) and blocking visible and infraredradiation (above 400 nm) from the beams of radiation reflected from thedichroic mirrors.

The preferred embodiment of the present invention that is illustrated inFIGS. 1, 2, and 3 has six light collecting assemblies surrounding lamp14 that develop six beams of ultraviolet radiation. It will beunderstood that a different number of light collecting assemblies may beused and that the number of light collecting assemblies chosen is adesign choice that is determined by the particular application of thepresent invention as are other choices of design.

Lamp 14, preferably, is adjustable, relative to the light collectingassemblies 16, in the X and Y (radial) directions and in the Z (axial)direction. In FIG. 2, there are illustrated a shaft 26 and a threadedmember 28, in threaded engagement with a block 30 mounted in the bottomportion 12 b of housing 12, for aligning lamp 14 in the Z (axial)direction. Similar means (not shown) may be provided for radialalignment of lamp 14 in the X and Y (radial) directions.

The sunlight simulators illustrated in FIGS. 1 through 4 also include aplurality of light guides, each positioned to receive individually fromthe light collecting means one of the beams of radiation, for conductingthe beams of radiation away from light collecting means. For theembodiment of the present invention illustrated in FIGS. 1, 2, and 3,the light guides are liquid light guides 32. For the embodiment of thepresent invention illustrated in FIG. 4, the light guides are fiberoptic light guides 34.

In the FIG. 4 embodiment of the present invention, in which the lightguides are fiber optic light guides, the light collecting means includea parabolic or ellipsoidal reflector 35 for reflecting the radiationemitted from lamp 14 to a first dichroic mirror 36, disposed at an angleof 45° with respect to the axis of the lamp, which, in turn,predominantly reflects ultraviolet radiation reflected from thereflector through a blocking filter 37 to a second dichroic mirror 38which also is disposed at an angle of 45° with respect to the axis ofthe lamp and reflects ultraviolet radiation reflected from dichroicmirror 36 further reducing the proportion of infrared and visibleradiation in the beam. Other portions of the spectrum are transmittedonto heat sinks 39 and 40. Also included in the light collecting meansof this embodiment of the present invention is a collimating lensassembly 41.

The preferred embodiment of the present invention that is illustrated inFIG. 4 has light collecting means that develop a single beam ofultraviolet radiation that is split into six beams of ultravioletradiation at the input ends 34 a of six fiber optic light guides which,for this embodiment of the present invention, are considered parts ofthe light collecting means. It will be understood that a differentnumber of fiber optic light guides may be used and that the number offiber optic light guides that are chosen is a design choice that isdetermined by the particular application of the present invention as areother choices of design.

Liquid light guides 32 in the FIGS. 1, 2, and 3 embodiment and fiberoptic light guides 34 in the FIG. 4 embodiment conduct the beams ofradiation away from the light collecting means. As shown in FIGS. 1, 5Aand 5B, the output ends 32 b of liquid light guides 32 are individuallyconnected to a plurality of blocks 42 and, as shown in FIG. 4, theoutput ends 34 b of fiber optic light guides 34 are individuallyconnected to a plurality of blocks 42.

A sunlight simulator, constructed in accordance with the presentinvention, further includes a plurality of optical homogenizer units 44,each positioned to receive individually from one of the light guides(liquid light guides 32 in FIGS. 1 and 2 or fiber optic light guides 34in FIG. 4) one of the beams of radiation, for providing a plurality ofadjustably positionable beams of radiation having uniform outputintensity profiles measured across the ends of the optical homogenizerunits. Optical homogenizer units 44 are connected to the opposite endsof blocks 42 from the output ends of the light guides.

As shown most clearly in FIGS. 5A, 5B, and 6, each optical homogenizerunit 44 includes an elongated tube 46 having, for example, a circularcross-section and a multisided elongated optical homogenizer 48 having alength equal to the length of tube 46. Tube 46 is made of a biologicallycompatible material, for example stainless steel. Optical homogenizer 48is positioned within tube 46 and, preferably, is made of a suitablequartz material core member 48 a (e.g., fused silica) having anevaporated aluminum coating 48 b deposited on the longitudinal surfacesof the core member. The evaporated aluminum coating 48 b serves tointernally reflect the radiation as it passes through the length of coremember 48 a.

The spaces between the longitudinal surfaces of optical homogenizer 48and the inner surface of tube 46 are filled with a suitable fillermaterial 50, such as a medical grade sealing material, to fix theposition of optical homogenizer in the tube. A suitable epoxy sealerlayer 52, preferably, is applied over the evaporated aluminum coating 48b of optical homogenizer 48 to protect the evaporated aluminum coating.

While optical homogenizer 48 is illustrated as having a squarecross-section, it may take other shapes dependent on the application ofthe sunlight simulator. Likewise, the choice of materials used to formoptical homogenizer 48 is dependent on the application of the sunlightsimulator.

A sunlight simulator, constructed in accordance with the presentinvention, further includes dosage regulating means for controlling thedoses of radiation provided by optical homogenizer units 44. For theembodiment of the invention as illustrated in FIGS. 5A, 5B, and 7, thedosage regulating means include a sensor 54, mounted in one of theblocks 42 transverse to the beam of radiation passing to the associatedoptical homogenizer unit 44, for monitoring the intensity of the beam ofradiation received by one of the optical homogenizer units 44 andcontrol means responsive to the sensor for individually blocking thepassage of each beam of radiation received by the optical homogenizerunits when each dose of the radiation provided by each opticalhomogenizer unit reaches a preset level. For the embodiment of thepresent invention being described, the control means of the dosageregulating means include a plurality of shutter assemblies 56, oneassociated with each of the optical homogenizer units 44. Each shutterassembly includes a shutter 58 that is movable, as indicated by arrows57 a and 57 b, into and out from a first recess 42 a that extends acrossblock 42 transverse to the beam of radiation. Shutter 56 is movablebetween a first position, as illustrated in FIG. 5A, at which the beamof radiation is allowed to pass to optical homogenizer unit 44 andsecond position, as illustrated in FIG. 5B, at which the beam ofradiation is blocked from passing to the optical homogenizer unit. Eachshutter assembly 56 also includes a solenoid 60 and a solenoid plunger62 to which shutter 58 is affixed, so that when the solenoid isdeactuated and the solenoid plunger is permitted to move out of thesolenoid, the shutter moves from the first position illustrated in FIG.5A to the second position illustrated in FIG. 5B. When solenoid 60 isactuated, the solenoid plunger is urged to move back into the solenoidand shutter 58 moves from the position illustrated in FIG. 5B to theposition illustrated in FIG. 5A.

Solenoid 60 can be arranged with permanent magnets in mutual repulsionforcing shutter 58 downwardly into a default position to block the beamof radiation. Permanent magnets having like poles in opposition producea magnetic force causing the magnets to repulse each other. The magneticattractive force of an actuated solenoid that maintains shutter 58 inthe upper position is stronger than the mutual repulsive force of thepermanent magnets when solenoid 60 is actuated. When the solenoid 60 isdeactuated, it no longer maintains shutter 58 in the retracted or upperposition and the repulsing force between the opposing permanent magnetsforces the shutter to move downward and assume the default or blockedposition.

Sensor 54, preferably, is a piano-piano quartz blank 54 a which may becircular, as illustrated in FIG. 7, or square or any appropriate shapethat has the prescribed area and thickness. The optically flat andparallel opposing major faces of the piano-piano quartz blank 54 ashould be polished to full optical clarity and be devoid of anycoloration, pigmentation, and shading and have a low surface RMS. Theedge surfaces of piano-piano quartz blank 54 a preferably are polishedwith the edge surfaces being 90° to the face surfaces and coated withaluminum mirror material. If circular, the piano-piano quartz blank 54 ashould have one area of the circumferential edge a chord that ispolished and has sufficient flat area to receive a photosensor 54 b thatdevelops a signal representative of the intensity of the beam ofradiation passing through the sensor.

The control means of the dosage regulating means also include meansresponsive to sensor 54 for individually actuating solenoids 60 to moveshutters 58 to the second positions to block the beams of radiationpassing through shutter assemblies 56 when the doses of radiationprovided by the associated optical homogenizer units 44 reach the presetlevels. The control means may be a central processing unit (CPU) thatreceives signals from sensor 54 that are representative of the intensityof the beam of radiation passing through the sensor and integrates overtime the amount of radiation passing through the sensor. When the totalradiation passing through the sensor reaches a preset level, the CPUenergizes solenoid 60 which, in turn, drives solenoid plunger 62 andshutter 58 away from the solenoid (downward as illustrated in FIGS. 5Aand 5B) from the position illustrated in FIG. 5A to the positionillustrated in FIG. 5 b to block the beam of radiation passing throughshutter assembly 56.

In one embodiment of the present invention, a single sensor 54associated with one of the shutter assemblies 56 serves to actuateshutter 58 with which it is associated and the other shutters 58 in theother shutter assemblies 56. This can be accomplished by determining, inadvance, the intensities of the beams of radiation developed by thelight collecting means, entering data representative of the relativebeam intensities in the CPU, and programming the CPU to actuatesolenoids 60 individually at the appropriate times based on theradiation dosage determined by the CPU from the signals received fromsensor 54.

In a second embodiment of the present invention, the dosage regulatingmeans includes a plurality of sensors 54, one mounted in each block 42,which are individually associated with each shutter assembly 56, forindividually monitoring the intensities of the beams of radiation. TheCPU integrates individually over time the amount of radiation passingthrough each sensor 54 and individually actuates each solenoid 60 in theassociated shutter assembly 56.

In a third embodiment of the dosage regulating means that functionswithout any sensor for monitoring the intensity of any of the beams ofradiation, shutters 58 block the beams of radiation at prescribed timesthat are programmed in the CPU. The CPU functions as a timing circuitthat individually actuates solenoids 60 at times determined in advancethat are based on determining, in advance, the intensities of the beamsdeveloped by the light collecting means.

Instead of locating shutters 58, solenoids 60, and solenoid plungers 62between the light guides and the optical homogenizer units (i.e., at theoutput ends of the light guides), the shutters, solenoids, and solenoidplungers can be located between the light collecting means and the lightguides (i.e., at the input ends of the light guides) as shown by dashedlines in FIG. 1. With shutters 58, solenoids 60, and solenoid plungers62 located as illustrated by the dashed lines in FIG. 1, a solenoid,when deactuated, permits the associated solenoid plunger and shutter tomove into a recess 63 a in a block 63 and, when the solenoid isactuated, the associated solenoid plunger and shutter are urged to moveout of recess 63 a to regulate the dosage of radiation delivered by theassociated homogenizer unit.

A sunlight simulator, constructed in accordance with the presentinvention, preferably further includes attenuator means for individuallyand selectively regulating the intensity of each of the beams ofradiation developed by the light collecting means. In one preferredembodiment of the present invention, the attenuator means include aplurality of individual attenuators 64, one for each beam of radiationdeveloped by light collecting means, with each attenuator disposedeither between one of the light guides and one of the opticalhomogenizer units as illustrated in FIGS. 5A and 5B, or between one ofthe light collecting assemblies and one of the light guides, asillustrated in FIG. 2.

Referring to FIGS. 5A and 5B, each attenuator 64 is movable within asecond recess 42 b (not shown in FIG. 5B) that extends across block 42transverse to the beam of radiation. The penetration of each attenuator64 in one of the recesses 42 b is individually adjustable, for exampleby the turning of a thumb screw 66 having a point end that bears againstblock 42, to selectively restrict the amount of radiation received bythe associated optical homogenizer unit.

One form of an attenuator that can be used in the present invention isillustrated by FIGS. 5A and 5B. This attenuator has through openingsthat vary in size to vary the intensity of a beam of radiation passingthrough the attenuator as the penetration of the attenuator into therecess 42 b in block 42 is adjusted. As illustrated by FIGS. 5A and 5B,one form of an attenuator 64 has opaque horizontal bars that areseparated by open horizontal spaces that decrease in width moving alonga length of the attenuator from bottom to top. In another form ofattenuator 64 as illustrated in FIG. 8, the open spaces are horizontalrows of circular openings with the diameters of the openings decreasingmoving along a length of the attenuator from bottom to top.

An alternative form of an attenuator is illustrated by FIGS. 9A and 9B.This embodiment of the attenuator includes a spring 68 that ispositioned in recess 42 b in block 42. Spring 68 is compressible andexpandable within recess 42 b to vary the space between the sectors ofthe spring. Spring 68 is compressed and expanded by the turning of athumb screw 70 having a point end that bears against block 42 toselectively restrict the amount of radiation received by the associatedoptical homogenizer unit.

It is apparent from the foregoing that an attenuator that can be used ina sunlight simulator constructed in accordance with the presentinvention can take a variety of forms. Besides those attenuators thathave been described above that have open spaces that decrease in sizemoving along a length of the attenuator from bottom to top (e.g., FIGS.5A, 5B, and 8) and those that have uniform size open spaces (e.g., FIGS.9A and 9B), the open spaces may decrease in size and then increase insize moving along the length of the attenuator. A major consideration inselecting the form of the attenuator is the nature of the associatedoptical homogenizer unit and the nature of the beam of radiation that isreceived by the associated optical homogenizer unit.

As indicated in FIG. 2, the attenuator means can be disposed between thelight collecting means and the light guides. In FIG. 2, thumb screws 72individually control the positions of attenuators 74.

Also, instead of setting the positions of attenuators 74 manually, forexample, by thumb screws 66, 70 or 72, the positions of the attenuatorscan be set by suitable drives that are controlled, for example, by theCPU programmed or set to achieve the desired attenuation of the beams ofradiation.

Referring to FIGS. 10 and 10A, the ends of optical homogenizer units 44are fixed in a block 76 that is adapted to be placed against a subjectthat is to be exposed to the radiation provided by the homogenizersunits. Preferably, the subject contact surface 76 a of block 76 istreated so that the subject experiences no discomfort (e.g., abrasion,temperature extremes, etc.) when the subject contact surface 76 a isplaced against the subject and the subject is exposed to radiationhaving uniform output intensity profiles measured across the ends of theoptical homogenizer units.

As shown most clearly in FIG. 10A, for the embodiment of the probe endbeing described, block 76 is composed of a heat sink 78, a coolingsource 80, and a front cover 82. The ends of optical homogenizer units44 are brought together and fitted in block 76. Heat sink 78, coolingsource 80, and front cover 82 have aligned openings through whichoptical homogenizer units 44 project, so that a subject receives theradiation provided by the optical homogenizer units.

Heat sink 78 serves to relieve heat generated both by artifact infraredradiation and heat dispelled by block 76. Cooling source 80, preferablya Peltier device, is electrically polar oriented such that the surfaceof the cooling source facing the output remains a cooling surface.Cooling source 80 has means for developing an indication of the skintemperature of the subject that controls the temperature of the coolingsource. Such means, represented by reference numeral 84, can include atemperature sensor, a thermocouple, or a resistance temperaturedetector, a pair of lead wires 86 a, 86 b connected to the CPU, and apair of lead wires 88 a, 88 b from the system power supply (PS). Thesignals from sensing means 84 are conducted to the CPU which, in turn,controls the system power supply to maintain cooling source 80 at thedesired temperature. Front cover 82, preferably composed of a highdielectric, medically acceptable polymer that is non-reactive to theskin of a subject and has high resistance to electrical transmission andhigh thermal conductivity, has an opening 90 through which the sensingmeans 84 in cooling source 80 are exposed to the skin of the subject todevelop an indication of the skin temperature of the subject.

While preferred embodiments of the invention have been shown anddescribed herein, it will be understood that such embodiments areprovided by way of example only. Numerous variations, changes andsubstitutions will occur to those skilled in the art without departingfrom the spirit of the invention. Accordingly, it is intended that theappended claims cover all such variations as fall within the spirit andscope of the invention.

1. Dosage regulating apparatus for a sunlight simulator for controllingthe doses of radiation developed by the sunlight simulator, saidapparatus comprising: a sensor for monitoring the intensity of a beam ofradiation developed by said sunlight simulator; and control meansresponsive to said sensor for blocking the passage of the beam ofradiation when the dose of radiation developed by said sunlightsimulator reaches a preset level.
 2. Dosage regulating apparatusaccording to claim 1 wherein said control means include: (a) a shutterassembly having: (1) a shutter movable between a first position forallowing the beam of radiation to pass therethrough and a secondposition for blocking passage of the beam of radiation, (2) a solenoidplunger to which said shutter is affixed and with which said shutter ismovable between said first position and said second position, and (3) asolenoid for moving said solenoid plunger and said shutter between saidfirst position and said second position; and (b) means responsive tosaid sensor for actuating said solenoid to move said shutter to saidsecond position to block the beam of radiation passing through saidshutter assembly when the dose of radiation developed by said sunlightsimulator reaches the preset level.
 3. Dosage regulating apparatus for asunlight simulator for controlling the doses of radiation developed bythe sunlight simulator, said apparatus comprising: a shutter assemblyhaving: (a) a shutter movable between a first position for allowing abeam of radiation to pass therethrough and a second position forblocking passage of the beam of radiation therethrough, (b) a solenoidplunger to which said shutter is affixed and with which said shutter ismovable between said first position and said second position; and (c) asolenoid for moving said solenoid plunger and said shutter between saidfirst position and said second position; and a timing circuit foractuating said solenoid to move said shutter to said second position toblock the beam of radiation passing through said shutter assembly at aprescribed time.